Road safety is a very important issue today. Constant speed monitoring of vehicles on the road network is one of the most perspective fields of road safety. This allows collecting various data, both for individual objects and traffic flow as a whole. The analysis of these data will allow predicting emergencies more effectively and also to improve the general control over the movement of motor transport. One of the ways of constant monitoring of vehicle speed is the use of modern GPS navigation systems. The article presents the results of research on the possibility of using GPS navigation device as part of the monitoring system for the speed of vehicles. Experimental data on vehicle speed measurement with the help of GPS navigation device have been obtained. Also, errors in speed measurement have been estimated. For this purpose, the speed data from the GPS navigation device have been compared with the speed data, which have been obtained as follows. The video camera recorded moments when the object crossed some control points. The distance between them was recorded and known in advance. The time was calculated from the video footage. Thus, knowing the time spent on the passage between the two control points, it was possible to determine the speed of the object with which the experimental data have been compared. It has been found that the variations in the motor transport speed in indications of the GPS navigation devices had small values. Also, experimental data of speed measuring with GPS navigation device at acceleration and braking of objects have been presented in the research. It was found that in these cases occurs the data update with time delay in the range from 2 to 6 seconds. Therefore, there may be significant inaccuracies in determining the speed of vehicles, which will reduce the efficiency of the GPS navigation device in case of traffic jams. It is assumed that this phenomenon is associated with speed measurement software features in a GPS navigation device that takes into account errors measurement of the object coordinates. Therefore, to better control the movement of objects under these conditions, additional means are required, which should be installed in the places with the highest probability of traffic violations.